Rubber compositions containing tackifiers

ABSTRACT

A composition comprising, a rubber component selected from the group consisting of a rubber polymer, a synthetic rubber polymer, and combinations thereof; and an alkylphenol resin which is a reaction product of: at least one phenolic monomer selected from the group consisting of phenol, cresol, resorcinol, xylenol, ethyl phenol, alkylresorcinols, and combinations thereof; and at least one alkyl aldehyde having from 5 to 12 carbon atom alkyl groups, is disclosed. The composition can be used to prepare articles of manufacture such as tires, tire treads, tire shoulders, tire sidewalls, rubber belts, and rubber hoses.

RELATED APPLICATION DATA

This application is a continuation application of co-pending U.S.application Ser. No. 15/727,329, with a filing date of Oct. 6, 2017, ofwhich the entire content of the co-pending application is incorporatedby reference herein.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to rubber compositions. The invention particularlyrelates to rubber compositions that contain tackifiers.

Background

Typically, alkylphenol resins derived from condensing octylphenol ornonylphenol with formaldehyde are used in tire and rubber compositionsas tackifiers. However, octylphenols and nonylphenols have recently beensubject to regulatory control. Octylphenols are known to be ofenvironmental concern. In Europe, para-tert-octylphenol has beenclassified as a Category-1 Acute and Chronic Environmental Hazard.Additionally, it is recommended that the use of octylphenols be phasedout under the OSPAR Convention, and it is listed as a substance forpriority action under the Helsinki Convention, which protects the marineenvironments of the north-east Atlantic Ocean and Baltic Searespectively.

Nonylphenols are also of environmental concern. The United StatesEnvironmental Protection Agency has taken the position that nonylphenolpersists in the environment, particularly in the aquatic environment andthat it is moderately bioaccumulative and extremely toxic to aquaticorganisms. It is also the Environment Protection Agency's position thatnonylphenol exhibits estrogenic properties in both in vitro and in vivoassays.

On Sep. 25, 2014, the Environmental Protection Agency proposed aSignificant New Use Rule to require an in-agency review before amanufacturer starts or resumes use of 15 nonylphenols (NPs) andnonylphenol ethoxylates (NPEs). Therefore, tackifiers prepared fromalkylphenol resins having little or no octylphenol or nonylphenolmonomers would be desirable.

SUMMARY

In one broad embodiment of the invention, there is disclosed acomposition comprising, consisting of, or consisting essentially of arubber component selected from the group consisting of a rubber polymer,a synthetic rubber polymer, and combinations thereof; and an alkylphenolresin which is a reaction product of: at least one phenolic monomerselected from the group consisting of phenol, cresol, resorcinol,xylenol, ethyl phenol, alkylresorcinols, and combinations thereof; andat least one alkyl aldehyde having from 5 to 12 carbon atom alkylgroups.

Also disclosed is an article of manufacture prepared using theabove-mentioned composition wherein the article is selected from thegroup consisting of a tire, a tire tread, a tire shoulder, a tiresidewall, a rubber belt, and a rubber hose.

Also disclosed is the use of an alkylphenol resin which is a reactionproduct of: at least one phenolic monomer selected from the groupconsisting of phenol, cresol, resorcinol, xylenol, ethyl phenol,alkylresorcinols, and combinations thereof; and at least one alkylaldehyde having from 5 to 12 carbon atom alkyl groups in a compositioncomprising a rubber component selected from the group consisting of arubber polymer, a synthetic rubber polymer, and combinations thereof.

Description

In the present invention, there is disclosed a composition comprising,consisting of, or consisting essentially of a rubber component selectedfrom the group consisting of a rubber polymer, a synthetic rubberpolymer, and combinations thereof; and an alkylphenol resin which is areaction product of: at least one phenolic monomer selected from thegroup consisting of phenol, cresol, resorcinol, xylenol, ethyl phenol,alkylresorcinols, and combinations thereof; and at least one alkylaldehyde having from 5 to 12 carbon atom alkyl groups.

The alkylphenol resin is a reaction product of at least one alkylaldehyde and at least one phenolic monomer selected from the groupconsisting of phenol, cresol, resorcinol, xylenol, ethyl phenol, alkylresorcinols, isomers thereof, and combinations thereof. Suitable isomersinclude ortho-, meta-, and para-isomers, such as ortho-, meta-, andpara-cresol.

For the purposes of the application, alkyl resorcinols are dihydroxybenzenes having one or two alkyl chains present on the ring. The alkylchains can have from 1 to 3 carbons.

The alkyl aldehydes that can be used are any aldehydes having from 5 to12 carbon atom alkyl groups. In various embodiments, the alkyl aldehydescan be selected from the group consisting of 3,5,5-trimethyl hexanal,nonanal, 2-ethyl hexanal, and combinations thereof.

The alkylphenol resins can be in the form of novolac and resole resins.Resole resins are formed when prepared using a base catalyst andnovolacs when prepared using an acid catalyst.

Also, with the reaction of the phenolic monomer with an alkyl aldehydeto produce alkylphenol resins, the molar ratio of the reactants used inreaction can, in various embodiments, determine the molecular structureand physical properties of the resin. When it is desirable to prepare anovolac type resin, an aldehyde:phenol ratio between 0.5:1 and 1:1 (suchas 0.5:1 to 0.8:1) with an acid catalyst will form novolac resins, whichare thermoplastic in character. A higher aldehyde:phenol ratio (forexample, more than 1:1 to 3:1) with a base catalyst will form resoleresins, which are characterized by their ability to be thermallyhardened at elevated temperatures.

In various embodiments, the alkylphenol resin is in the form of aformaldehyde free resin. For formaldehyde free alkylphenol resins, themole ratio of aldehyde to phenolic monomers can be from about 0.75:1 toabout 0.9:1, for example, 0.85:1. Alkylphenol resins free offormaldehyde have a molecular weight (Mw) of less than 2000 Daltons,such as from 1000 to less than 2000 Daltons.

In another embodiment, formaldehyde is used to form the alkylphenolresin. The formaldehyde-containing alkylphenol resins can be a novolacresin and a resole resin. The novolac resin can have a molecular weightfrom 2000 Daltons to 50000 Daltons and a resole resin can have amolecular weight from 2000 Daltons to 20000 Daltons.

The alkylphenol resins of the composition are free or substantially freeof octylphenol or nonylphenol monomers. These resins can also be madefree of formaldehyde.

Further information about alkylphenol resins and their preparation canbe found in United States Patent Application Publication No.2017/0121443, which is herein incorporated by reference in its entirety.

The alkylphenol resin can be present in the composition in the range offrom 1 phr to 10 phr, from 2 phr to 8 phr in various embodiments, andfrom 2 phr to 6 phr in various other embodiments. ‘Phr’ stands for‘parts per hundred rubber.’

The composition of the application contains at least one polymerselected from the group consisting of a rubber polymer, a syntheticrubber polymer, and combinations thereof.

Natural rubber comprises polymers of isoprene. It is harvested in theform of a latex from rubber trees.

Synthetic rubbers can also be present in the composition. Syntheticrubbers are polymers synthesized from petroleum byproducts. Examples ofsynthetic rubber include, but are not limited to styrene butadienerubber, polybutadiene rubber, halogenated butyl rubber, butyl rubber,polyisoprene rubber, styrene/isoprene/butadiene rubbers, andcombinations thereof. In various embodiments, the rubber component canbe hydrogenated or partially hydrogenated.

In various embodiments, when synthetic rubber and natural rubber arepresent in the composition together, they are present in a ratio of 9parts synthetic rubber to 1 part natural rubber, 4 parts syntheticrubber to 1 part natural rubber in various embodiments, and 3 partssynthetic rubber to 2 parts natural rubber in various other embodiments.

The composition can also contain various types of chemicals typicallyused in the rubber industry. Examples include, but are not limited tovulcanizing agents, vulcanizing accelerators, antioxidants, pigments,and fillers.

The composition can be used to manufacture articles including but notlimited to a tire, a tire tread, a tire shoulder, a tire sidewall, arubber belt, and a rubber hose. The articles can be manufactured by anymethod known in the art.

The composition of the present application has a Shore A Hardness asmeasured by ASTM D2240 in the range of from 40 to 65, from 45 to 60 invarious embodiments, and from 47 to 50 in various other embodiments.

The composition has a tensile strength as measured by ASTM D412 in therange of from 1700 to 2800 psi, from 2000 to 2700 psi in variousembodiments, and from 2100 to 2600 psi in various other embodiments.

The composition has a Subjective Tack Test rating as measured by thethumb tack test (where 1 is the lowest rating and 10 is the highestrating) in the range of from 1 to 9, from 2 to 8 in various embodiments,and from 2 to 7 in various other embodiments.

For a tire to have a good wet grip and skid resistance, it is desiredthat the composition have a high tan δ at the temperatures of from 0° C.to 30° C. Additionally, for a tire to have low resistance to rolling,thereby providing better gas mileage, it is desirable that thecomposition have a low tan δ between the temperatures of from 60° C. to80° C.

The composition has a tan δ at 0° C. as measured by Dynamic MechanicalAnalysis (DMA) in the range of from 0.12 to 0.17, from 0.13 to 0.16 invarious embodiments, and from 0.14 to 0.16 in various other embodiments.

The composition has a tan δ at 60° C. as measured by DMA in the range offrom 0.10 to 0.16, from 0.11 to 0.14 in various embodiments, and from0.11 to 0.13 in various other embodiments.

The composition has an ultimate elongation as measured by ASTM D412 inthe range of from 550% to 800%, from 620% to 750% in variousembodiments, and from 650% to 700% in various other embodiments.

The composition has a Mooney viscosity as measured by ASTM D1646 in therange of from 30 MU to 55 MU, from 35 to 50 MU in various embodiments,and from 40 to 47 MU in various other embodiments.

The composition has an elastic modulus at 60° C. as measured by DMA inthe range of from 3.60×10⁶ Pa to 5.00×10′ Pa, from 4.00×10⁶ Pa to4.80×10⁶ Pa in various embodiments, and from 4.05×10′ Pa to 4.75×10⁶ Pain various other embodiments.

EXAMPLES

The following examples are provided to illustrate the invention. Theexamples are not intended to limit the scope of the invention.

Example 1

A two liter flask was charged with 169.4 grams of phenol (1.800 moles)and 1.69 grams of dodecylbenzenesulfonic acid (DDBSA). The reactionmixture was heated to 130° C. and 230.8 grams of 2-ethylhexanal (1.800moles) was added over 60 minutes. The temperature was maintained at 130°C. by azeotropic distillation and the removal of generated water andwith 2-ethylhexanal returning to the flask. After the feed was complete,the reaction temperature was increased to 150° C. with the azeotropicremoval of water and was maintained for 2 hours. The temperature wasthen raised to 160° C. with the azeotropic removal of water and wasmaintained until the reaction was complete. The reaction mixture wasthen neutralized with 0.97 grams of 50% sodium hydroxide. The reactionmixture was then atmospherically distilled to 180° C. and furthervacuumed distilled to 28 inches of mercury and 190° C. to remove phenolrich distillate. Product characterization data is provided in Table 1,below.

Example 2

A one liter flask was charged with 182.0 grams of phenol (1.934 moles)and 1.82 grams of DDBSA. The reaction mixture was heated to 130° C. and223.2 grams of 2-ethylhexanal (1.741 moles) was added over 60 minutes.The temperature was maintained at 130° C. by azeotropic distillation andthe removal of generated water and with 2-ethylhexanal returning to theflask. After the feed was complete, the reaction temperature wasincreased to 150° C. with the azeotropic removal of water and wasmaintained for 2 hours. The temperature was then raised to 160° C. withthe azeotropic removal of water and maintained until the reaction wascompleted. The reaction mixture was then cooled to 130° C. underatmospheric reflux and 15.7 grams of 37% Formaldehyde (0.1934 moles) wasadded over 15 minutes. The temperature was held under reflux for 1 hour.The reaction mixture was then neutralized with 0.97 grams of 50% sodiumhydroxide. The reaction mixture was then atmospherically distilled to180° C. and further vacuumed distilled to 28 inches of mercury and 190°C. to remove phenol rich distillate. The product characterization datais provided in Table 1, below.

Example 3

A one liter flask was charged with 182.0 grams of phenol (1.934 moles)and 1.82 grams of DDBSA. The reaction mixture was heated to 130° C. and128.1 grams of 2-ethylhexanal (1.64 moles) was added over 60 minutes.The temperature was maintained at 130° C. by azeotropic distillation andthe removal of generated water and with 2-ethylhexanal returning to theflask. After the feed was complete, the reaction temperature wasincreased to 150° C. with the azeotropic removal of water and wasmaintained for 2 hours. The temperature was then raised to 160° C. withthe azeotropic removal of water and maintained until the reaction wascompleted. The reaction mixture was then cooled to 130° C. underatmospheric reflux and 23.5 grams of 37% Formaldehyde (0.29 moles) wasadded over 15 minutes. The temperature was held under reflux for 1 hour.The reaction mixture was then neutralized with 0.97 grams of 50% sodiumhydroxide. The reaction mixture was then atmospherically distilled to180° C. and further vacuumed distilled to 28 inches of mercury and 190°C. to remove phenol rich distillate. The product characterization datais provided in Table 1, below.

Example 4

A one liter flask was charged with 182.0 grams of phenol (1.934 moles)and 1.82 grams of DDBSA. The reaction mixture was heated to 130° C. and173.1 grams of 2-ethylhexanal (1.35 moles) was added over 60 minutes.The temperature was maintained at 130° C. by azeotropic distillation andthe removal of generated water and with 2-ethylhexanal returning to theflask. After the feed was complete, the reaction temperature wasincreased to 150° C. with the azeotropic removal of water and wasmaintained for 2 hours. The temperature was then raised to 160° C. withthe azeotropic removal of water and maintained until the reaction wascompleted. The reaction mixture was then cooled to 130° C. underatmospheric reflux and 47.1 grams of 37% Formaldehyde (0.58 moles) wasadded over 15 minutes. The temperature was held under reflux for 1 hour.The reaction mixture was then neutralized with 0.97 grams of 50% sodiumhydroxide. The reaction mixture was then atmospherically distilled to180° C. and further vacuumed distilled to 28 inches of mercury and 190°C. to remove phenol rich distillate. The product characterization datais provided in Table 1, below.

Example 5

A one liter flask was charged with 175.5 grams of phenol (1.864 moles)and 0.91 grams of 99% methane sulfonic acid (MSA). The reaction mixturewas heated to 130° C. and 167.7 grams of 2-ethylhexanal (1.308 moles)and 79.2 grams of 3,5,5-trimethylhexanal (0.557 moles) was added over 60minutes. Temperature was maintained at 130° C. by azeotropicdistillation and the removal of generated water and with 2-ethylhexanaland 3,5,5-trimethylhexanal returning to flask. After feed, reactiontemperature was increased to 150° C. with the azeotropic removal ofwater and maintained for 2 hours. The temperature was then raised to160° C. with the azeotropic removal of water and maintained untilreaction was completed. Reaction mixture was then neutralized with 0.95grams of 50% sodium hydroxide. Reaction mixture was then atmosphericallydistilled to 180° C. and furthered vacuum distilled to 28 inches ofmercury and 190° C. to remove phenol rich distillate. Productcharacterization data is provided in Table 1, below.

TABLE 1 Characterization Data for Examples 1-5 Brookfield 2-Formaldehyde 3,5,5- Mw Viscosity Polymer Phenol, Ethylhexanal, (37/11),trimethylhexanal, by Softening Free @125° C., Example moles moles molesmoles GPC Point, ° C. Phenol, % cPs 1 1.80 1.80 NA NA 831 77 0.15 641 21.93 1.74 0.19 NA 949 90 0.09 2137 3 1.93 1.64 0.29 NA 1206 91 0.5 44504 1.93 1.35 0.58 NA 1752 100 0.25 6970 5 1.86 1.31 NA 0.56 993 81 0.11726

The tackifiers in Examples 1-5 were formulated with both natural rubberand synthetic rubber at 2, 4, and 6 phr. These compositions wereevaluated for several properties, along with compositions prepared froma para-tert-octylphenol-formaldehyde resin. A control compositioncontaining no tackifier was also prepared. The compositions wereprepared based on the formulation listed in Table 2, below.

TABLE 2 Rubber Composition Formulation Material Amount (phr) NaturalRubber TSR20 40.00 Synthetic Rubber High Cis BR 1207 60.00 Carbon BlackN660 50.00 Activator Zinc Oxide 2.00 Process Aid Stearic Acid 1.50Plasticizer Naphthenic Oil 8.00 Antiozonant 6PPD 1.50 Antioxidant TMQ1.00 Antidegradant Akrowax 5084 1.50 Accelerated TBBS 0.50 CurativeRubbermakers Sulfur 2.00

A description of the materials used is provided below:

TSR20: Technically Specified Rubber Grade 20

High Cis BR 1207: High cis-1,4 polybutadiene

N660: Carbon black

6PPD: N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine, an antiozonant

TMQ: 2,2,4-trimethyl-1,2-dihydroquinoline polymer, an antioxidant

Akrowax 5084: blend of microcrystalline wax and paraffin waxes,available from

Akrochem Corporation

The following test methods were used:

Shore A Hardness: ASTM D2240

Tensile Strength: ASTM D412

Subjective Tack: Subjective tack was determined by the thumb tack test.This is a subjective evaluation which is done by pressing a thumbbriefly into the sample. The rating is 1-10 (1—lowest, 10—highest).

Tan delta (δ) at 0° C. and 60° C.: Tan delta was determined by DynamicMechanical Analysis (DMA) using a RSA G2 analyzer from TA Instruments ata frequency of 10 Hz.

Elastic Modulus at 60° C.: Elastic modulus was determined by DMA using aRSA 02 analyzer from TA Instruments at a frequency of 10 Hz.

Ultimate Elongation: ASTM D412

Mooney Viscosity at 212° F.: ASTM D1646

The results of the tests are shown in Table 3 below.

TABLE 3 Test Results for Rubber Compositions Tackifier TensileSubjective Elastic Ultimate Mooney Resin Hardness Strength Tack Tan δ atTan δ at Modulus Elongation Viscosity Sample (phr) (points) (psi) Rating0° C. 60° C. [×10⁶] @60° C. (%) (MU) Control 0 50 2644 2 0.1295 0.10114.16 620 37.4 Reference A 2 49 2568 3 0.1613 0.1469 3.19 635 38.95Reference A 4 46 2329 4 0.1566 0.1197 3.69 660 36.97 Reference A 6 452329 6 0.167 0.1378 3.38 698 35.05 Example 1 2 48 2594 2 0.1323 0.1054.02 653 36.74 Example 1 4 48 2546 4 0.1474 0.1155 4.05 683 37.08Example 1 6 47 2436 7 0.1515 0.1318 3.71 676 38.54 Example 2 2 50 2558 20.1393 0.1157 4.51 634 47.37 Example 2 4 49 2374 5 0.1426 0.1313 4.27655 46.17 Example 2 6 48 2306 5 0.1539 0.1476 4.09 692 42.82 Example 3 249 2456 2 0.1317 0.1093 4.03 623 43.89 Example 3 4 49 2276 4 0.14190.1268 3.98 635 43.99 Example 3 6 48 2377 5 0.1516 0.1493 3.97 688 44.68Example 4 2 50 2587 2 0.1363 0.1188 4.83 713 47.64 Example 4 4 49 2298 20.1484 0.1381 4.78 700 45.42 Example 4 6 49 2129 2 0.1432 0.1527 4.91742 43.81 Example 5 2 50 2624 2 0.126 0.1043 4.06 654 42.35 Example 5 448 2460 6 0.1489 0.1235 4.09 663 41.57 Example 5 6 48 2438 7 0.1430.1332 3.87 686 40.63

As can be seen in Table 3 above, Examples 1-5 have hardness levels thatare comparable to or higher than the reference formulations.

Examples 1-5 additionally exhibit similar tensile strength to ReferenceA, with the exception of Example 1 at 6 phr loading.

Example 5 had higher tack values than Reference A at 4 phr and 6 phrloadings. Example 1 also had a higher tack value at 6 ph loading.

Examples 1-5 had lower tan δ values at 0° C. than Reference A. With tanδ at 60° C., Examples 1-5 had comparable values to the referenceexamples at 4 phr and 6 phr loadings, and lower values at 2 phr loading.

Example 4 had higher ultimate elongation than the reference examples.The ultimate elongation values for Examples 1-3 and 5 were comparable tothe reference examples.

Examples 1-5 exhibited higher viscosity over the control example.Example 1 had a viscosity that was comparable to Reference A.

Example 4 had the highest elastic modulus value at 60° C.

While the present invention has been described and illustrated byreference to particular embodiments, those of ordinary skill in the artwill appreciate that the invention lends itself to variations notnecessarily illustrated herein.

What is claimed is:
 1. A method of forming a composition, comprising:making a resole alkylphenol resin comprising: reacting at least onephenolic monomer selected from the group consisting of phenol, cresol,resorcinol, xylenol, ethyl phenol, alkylresorcinols, and combinationsthereof and at least one alkyl aldehyde having from 5 to 12 carbon atomalkyl groups in the presence of an acid catalyst, and optionally, anorganic solvent that forms an azeotrope with water; adding a basecatalyst and formaldehyde; reacting the at least one phenolic monomer,the at least one alkyl aldehyde, and the formaldehyde in the presence ofthe base catalyst; and performing a reflux or azeotropic distillationprocess; and adding the alkylphenol resin to a composition comprising arubber component.
 2. The method of claim 1, wherein the rubber componentis selected from the group consisting of a rubber polymer, a syntheticrubber polymer, and combinations thereof.
 3. The method of claim 1,wherein the alkylphenol resin acts as a tackifier.
 4. The method ofclaim 1, wherein the alkyl aldehyde is selected from the groupconsisting of 3,5,5-trimethyl hexanal, nonanal, 2-ethyl hexanal, andcombinations thereof.
 5. The method of claim 2, wherein the syntheticrubber polymer is selected from the group consisting of styrenebutadiene rubber, polybutadiene rubber, halogenated butyl rubber, butylrubber, polyisoprene rubber, styrene/isoprene/butadiene rubber, andcombinations thereof.
 6. The method of claim 1, wherein the compositionhas a tan δ at 0° C. as measured by Dynamic Mechanical Analysis in therange of from 0.12 to 0.17.
 7. The method of claim 6, wherein thecomposition has a tan δ at 60° C. as measured by Dynamic MechanicalAnalysis in the range of from 0.10 to 0.16.
 8. The method of claim 1,wherein the composition has an ultimate elongation as measured by ASTMD412 in the range of from 550% to 800%.
 9. The method of claim 1,wherein the composition has an elastic modulus at 60° C. as measured byDynamic Mechanical Analysis in the range of from 3.60×10⁶ Pa to 5.00×10⁶Pa.
 10. The method of claim 1, wherein the alkylresorcinols comprisedihydroxy benzenes having one or two alkyl chains present on a ring. 11.The method of claim 10, wherein the alkyl chains comprise from 1 to 3carbons.
 12. The method of claim 1, wherein the alkylphenol resin can bepresent in the composition in the range of from 1 to 10 parts perhundred rubber.